1. Field of the Invention
The present invention relates to a high-purity standard particles production apparatus and the same particles, especially, pertaining to a nanometer-sized standard particles production technique that is indispensable for verifying a particle counter that is used for controlling nanometer-sized high-purity particles and for measuring the collecting efficiency of a filter that is used for removing nanometer-sized impurity particles contained in the gas phase where a semiconductor or a liquid crystal is produced as well as to a production technique of nanometer-sized monodisperse high-purity standard particles that is prospective of various functional occurrences caused by quantum size effect.
2. Description of Prior Art
In the recent semiconductor industry, a pattern size in the nanometer scale of 0.13 xcexcm is to be soon realized while that of 0.18 xcexcm is in mass production. In accordance with the tendency to minify the pattern size, it requires that the remaining dusts present in the production process thereof that affect the yield of the production output be thoroughly controlled. Especially, not only nanometer-sized impurity particles containing such chemical components as heavy metal, carbon and so forth are in themselves capable of causing such inconveniences as the disconnection of a semiconductor device or the short-circuit thereof, but also contamination caused by the impurities dispersed during the heating treatment of the production process thereof gives significant affect on the quality control thereof, which should be held under thorough control.
On the other hand, observing nanometer-sized particles apart from the contamination thereof by impurities, the particle of 10 nm or below happens to show property or function that is not observed in the bulk state thereof. For instance, when such IV group elements as silicon (Si) and germanium (Ge), which elements are hard to emit light in the bulk state thereof because they are indirect transition semiconductors, turn to become the particles of several nanometers in size, it is known that those particles emit strong visible light in a room temperature. However, because the nanometer particle has large proportion of surface exposure atoms, which proportion amounts to 40% in the scale of 5 nm, it is extremely sensitive to the contamination of impurities and the occurrence of crystal defects so that it has been generally accepted that such particle is hard to be developed into a high-performance function device. Further, as the novel property and function of the particle as mentioned above is brought by a so-called quantum size effect or in accordance with the size thereof, it is required to put the size of the respective particles in order so as to obtain monodispersive particles for the purpose of enhancing such a novel function thereof as monochromatic light ejection and so forth.
Such nanometer-sized particles production methods as a colloidal method and an in-gas evaporation method are conventionally known. The colloidal method is arranged such that metallic salt is reduced in alcohol along with a polymer surface-active agent under reflux condition so as to generate metallic particles coated with the polymer compound in a colloidal state, which method belongs to a low-temperature synthetic method and is said to be easier to control the diameter of the particles so as to obtain the same in an uniform size in comparison with another similar methods. Then, such vapor-phase growth methods as the above in-gas evaporation method by means of arc discharge and resistance heating are arranged such that not only metal but also evaporable compound are evaporated and cooled in an inert gas so as to be formed into particles.
The nanometer-sized particles producible by the colloidal method are limited to the materials that are soluble in alcohol, and the particles as produced by the same method are coated with a polymer compound, the selectivity of which materials is an issue to be solved yet. Then, when the raw material of a high fusing point is an object for the above vapor-phase growth method or the in-gas evaporation method by means of arc discharge or resistance heating as mentioned above, the heating portion of the reaction chamber occupies a comparatively large space thereof and the possibility that the raw material reacts with a vaporizing pot can not be disregarded, so that it is hard to obtain high-purity particles keeping the stoichiometric composition of the raw material intact. In addition, the geometric standard deviation of the particle diameter distribution is comparatively large, so that it is difficult to put to use the particles as produced for monodispersive standard particles.
As mentioned above, in view of the prior art, a much cleaner and trouble-free production process is sought after in order to obtain high-purity standard particles of nm size in scale,
In view of the inconveniences encountered with the prior art, the present invention is to provide a high-purity standard particles production apparatus that allows nanometer-sized high-purity standard particles of monodispersive uniform structure, the material for which particles is wide in selection to be produced in an efficient manner with the abatement of contamination or damage thereon and the same particles.
The high-purity standard particles production apparatus according to the present invention comprises a particle generation chamber where high-purity particles are generated by laser ablation in an ambient gas, a particle classification chamber where high-purity standard particles of a diameter as required are classified from high-purity particles as generated in the particle generation chamber and a particle collecting chamber where high-purity standard particles as classified are collected.
This apparatus allows nanometer-sized high-purity standard particles of wide selectivity in material and monodispersive uniform structure to be produced and collected in an efficient manner with the abatement of contamination and damage thereon.
The present invention having the above characteristics is embodied in an apparatus comprising a particles generation chamber where high-purity particles are generated in an ambient gas by laser ablation, a particles classification chamber where high-purity standard particles of a diameter as required are classified from the high-purity particles generated in the generation chamber and a particles collecting chamber where the high-purity standard particles as classified are collected. This apparatus allows nanometer-sized high-purity standard particles of monodispersive uniform structure to be produced and collected in an efficient manner with the abatement of contamination and damage thereon.
Then, the particle classification chamber of the high-purity standard particles production apparatus according to the present invention is characterized in being provided with the plurality of particle classification means, which means make the distribution width of the diameter of the standard particles narrower.
Further, heating treatment by means of infrared radiation is performed on the high-purity standard particles at the downstream of the classification chamber of the apparatus according to the present invention, which makes spherical the high-purity standard particles having various shapes through cohesion and improves the crystallization thereof,
Then, the high-purity standard particles production apparatus according to the present invention is characterized in being provided with a gas refining means to substantially remove the impurities contained in a raw material gas supplied as an ambient gas, which restrains the impurities contained in such ambient gas as oxygen and the contamination of the particles as generated so as to highly purify the standard particles as produced.
Moreover, the particle collecting chamber of the high-purity standard particles production apparatus according to the present invention is characterized in being provided with an orifice that reduces the cross section of a piping system through the passage of the high-purity standard particles, which enlarges the difference in pressure between the upstream and downstream locations with regard to the orifice so as to improve the ejecting speed of the standard particles from the orifice and to augment the mobility of the standard particles as ejected from the orifice while to allow the particles to be deposited with concentration, with the result that the collecting efficiency of the nanometer-sized standard particles improves.
Then, the present invention realizes nanometer-sized high-purity standard particles as produced by the above production apparatus, which particles are provided with monodispersive uniform structure, irrespective of the kinds of material in use.
As described above, a high-purity standard particles production apparatus together with the same standard particles as produced is provided herein, which apparatus allows nanometer-sized high-purity standard particles of wide selectivity in material and monodispersive uniform structure to be produced in an efficient manner with the abatement of the contamination and damage thereof.
The means to solve the prior issue and the advantages brought thereby according to the present invention are described below in more details with reference to the accompanying drawings.